1. Field of the Invention
The present invention relates to, for example, a semiconductor, a transistor, and a semiconductor device. The present invention relates to, for example, a method for manufacturing a semiconductor, a transistor, and a semiconductor device. The present invention relates to, for example, a semiconductor, a display device, a light-emitting device, a lighting device, a power storage device, a memory device, a processor, and an electronic device. The present invention relates to a method for manufacturing a semiconductor, a display device, a liquid crystal display device, a light-emitting device, a memory device, and an electronic device. The present invention relates to a driving method of a semiconductor device, a display device, a liquid crystal display device, a light-emitting device, a memory device, and an electronic device.
Note that one embodiment of the present invention is not limited to the above technical field. The technical field of one embodiment of the invention disclosed in this specification and the like relates to an object, a method, or a manufacturing method. In addition, one embodiment of the present invention relates to a process, a machine, manufacture, or a composition of matter.
In this specification and the like, a semiconductor device generally means a device that can function by utilizing semiconductor characteristics. A display device, a light-emitting device, a lighting device, an electro-optical device, a semiconductor circuit, and an electronic device include a semiconductor device in some cases.
2. Description of the Related Art
As silicon which is used as a semiconductor of a transistor, either amorphous silicon or polycrystalline silicon is used depending on the purpose. For example, for a transistor included in a large display device, it is preferable to use amorphous silicon, which can be used to form a film on a large substrate with the established technique. For a transistor included in a high-performance display device where a driver circuit and a pixel circuit are formed over the same substrate, it is preferable to use polycrystalline silicon, which can be used to form a transistor having a high field-effect mobility. As a method for forming polycrystalline silicon, high-temperature heat treatment or laser light treatment which is performed on amorphous silicon has been known.
In recent years, transistors including oxide semiconductors (typically, In—Ga—Zn oxide) have been actively developed. The transistors including oxide semiconductors have different features from the transistors including amorphous silicon or polycrystalline silicon. For example, a display device to which a transistor including an oxide semiconductor is applied is known to have small power consumption.
It is known that a transistor including an oxide semiconductor has an extremely low leakage current in an off state. For example, a low-power-consumption CPU utilizing a characteristic of low leakage current of the transistor including an oxide semiconductor is disclosed (see Patent Document 1).
For reduction of power consumption by power gating, the transistor including an oxide semiconductor preferably has normally-off electrical characteristics. As a method for making the transistor including an oxide semiconductor have normally-off electrical characteristics by controlling the threshold voltage of the transistor, Patent Document 2 discloses a method in which a floating gate is provided in a region overlapping with the oxide semiconductor and a negative fixed charge is injected into the floating gate.
An oxide semiconductor film can be formed by a sputtering method or the like, and thus can be used in a transistor included in a large display device. Because a transistor including an oxide semiconductor has high field-effect mobility, a high-performance display device in which a driver circuit and a pixel circuit are formed over the same substrate can be obtained. In addition, there is an advantage that capital investment can be reduced because part of production equipment for a transistor including amorphous silicon or a transistor including polycrystalline silicon can be retrofitted and utilized.
Oxide semiconductors have a long history, and in 1985, synthesis of an In—Ga—Zn oxide crystal was reported (see Non-Patent Document 1). Further, in 1995, it was reported that an In—Ga—Zn oxide has a homologous structure and is represented by a composition formula InGaO3(ZnO)m (m is a natural number) (see Non-Patent Document 2).
In 1995, a transistor including an oxide semiconductor was invented, and its electrical characteristics were disclosed (see Patent Document 3).
In 2014, transistors including a crystalline oxide semiconductor were reported (see Non-Patent Documents 3 and 4). The transistors in these reports include a c-axis aligned crystalline oxide semiconductor (CAAC-OS) and thus are capable of mass-production and have high electrical characteristics and reliability.